Impaired cardiorespiratory function
Pulmonary function typically is compromised in the markedly obese, with restrictive lung disease and reduced functional residual capacity. If the patient smokes or has chronic obstructive lung disease, her pulmonary function is compromised even further, and her condition should be relayed to the anesthesiologist.
In addition, many obese patients have preexisting heart disease or conditions such as hyperlipidemia that put them at risk for heart disease. When evaluating an obese surgical patient, also ask about less apparent disorders, such as sleep apnea, which, if not addressed, may have grave postoperative consequences.
Preoperative evaluation and preparation
Goal: Assess and minimize risks
This process begins in the office or clinic with a discussion with the patient of any concerns and risks. The importance of early mobilization and ambulation after surgery should be emphasized. Any patient with uncontrolled diabetes or hypertension should continue to be monitored by her primary care physician. A patient who has not seen a physician recently should be assessed by an internist to ensure that no conditions go undetected before surgery.
Routine testing to start, but additional assessment may be justified. An obese patient should undergo the same routine testing as a woman of normal weight, but further testing may be warranted for any coexisting disorder. Because the obese patient may have a restrictive lung pattern by virtue of her body habitus, pulmonary-function testing is unlikely to yield new information and is probably not indicated—unless she smokes or has a history of chronic obstructive pulmonary disease. In that case, tests will clarify the obstructive component and bronchodilator response and are useful in postoperative management. Measurement of arterial blood gases is useful, however, because levels reflect respiratory function on a day-to-day basis.
Additional tests of cardiac status probably are not indicated on the basis of obesity alone. However, if initial tests (eg, the electrocardiogram) and the history suggest compromised cardiac function, two-dimensional echocardiography should be performed to determine the ejection fraction. Any concerns regarding cardiac function should be discussed with the anesthesiologist and cardiologist.
Because compromised pulmonary function is likely, I (Dr. Perkins) instruct each patient on the use of incentive spirometry before she undergoes anesthesia so that she has realistic expectations about the postoperative course. I also administer heparin at least 2 hours before induction (8 hours before induction if unfractionated heparin is used).6
If a hysterectomy or prolonged laparotomy is planned, prophylactic antibiotics are recommended.3 Thigh-high compression stockings or a pneumatic calf-compression device should be applied upon arrival in the operating room.
Anesthesia-related issues
Anticipate challenges involving the airway
The anesthesiologist’s primary concern in regard to the obese patient is establishment and maintenance of an airway to promote oxygenation. In morbidly and extremely morbidly obese patients, anatomic factors such as large breasts; a short, thick neck; large tongue; decreased mobility of the cervical spine; limited mouth opening; and greater amount of adipose tissue in the face and cheeks can render mask ventilation and intubation extremely difficult or impossible. Decreased functional residual capacity and tidal volume in the range of closing capacity may lead to extremely rapid oxygen desaturation when the patient is apneic.9
If the patient is pregnant, factors such as excess adipose tissue in the face become even more pronounced and increase the potential for catastrophe.
Appreciate mechanical concerns
The morbidly obese patient may exceed the weight limit of the operating table. In addition, placing her in a steep Trendelenburg position or rotating her laterally may compromise the integrity of the bed.
Coexisting disease, such as sleep apnea and acid reflux disease, should also be kept in mind. Compromised respiratory mechanics (eg, restrictive lung pattern) may cause further deterioration and make mechanical ventilation more difficult.
It also may be hard to establish vascular access, necessitating central venous line placement and introducing its associated risks.
Keep the anesthesiologist in the loop
In the postoperative period, obese patients face a heightened risk of complications related to diminished pulmonary function, such as oxygen desaturation, hypoventilation, and airway obstruction, which may lead to atelectasis, pneumonia, and pulmonary edema.10,11 For these reasons, early consultation with the anesthesiologist is recommended, especially if the initial evaluation suggests potential difficulties in securing the airway. In turn, the anesthesiologist should understand that, in some obese patients, even establishing a surgical airway may be difficult. Regional anesthesia should be considered when feasible.
Antacids and drugs that increase gastric motility have proved to be useful in minimizing aspiration-related risks.12,13
Surgical technique
Begin abdominal procedures by carefully choosing an incision
Do not base the decision solely on the degree of obesity, but also consider any additional procedures that are planned, such as lymph-node sampling. A vertical incision does permit greater exposure than is afforded by a transverse incision, but in some cases the latter may be more appropriate—even if the patient is morbidly obese.